• Composites Research
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• 제25권6호
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• pp.230-235
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• 2012

본 연구에서는 항공기용 카메라구조의 진동특성 파악하고 최적조건을 선정하여 구조의 경량화 설계 방안을 제시하였다. 다물체 동력학 프로그램인 ADAMS를 이용하여 모드해석을 진행하고, 해석 결과를 가지고 직교법을 이용하여 항공기용 카메라 구조의 경량화 및 최적조건을 선정하여 이전의 항공기용 카메라 구조와 모드해석 결과를 서로 비교하였다. 또한, 기존에 제시 되어진 베어링의 차원의 값을 무차원의 값으로 전환하여 보다 효과적인 베어링의 기준을 선정하였으며, 비교된 결과를 토대로 최적화된 항공기용 카메라 구조가 제안되었다.

• 한국군사과학기술학회지
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• 제21권3호
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• pp.264-278
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• 2018

The support structure of an optical mirror system is the one of the important design elements because the one affects the optical aberrations of the mirror surface. In this paper, Lagrange equation of the moving body of the fast steering mirror system(FSM) has been formulated to use with optimization design. Major goals for optimization are to assign the reasonably flexible stiffness to the structure and to enhance the first natural frequency of the mirror and support system in aid of more affordable control bandwidth for the FSM. Pursuing these purposes with the proposed method, the finite element analysis(FEA), optimization technique and the Zernike polynomial estimation are used for the design effects. It is concluded that the proposed approach for design well guides toward the desired design goals with regards to both structural and optical performances.

• 한국시뮬레이션학회논문지
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• 제25권1호
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• pp.1-9
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• 2016

본 연구는 공대공 미사일 조종날개의 공력 및 구조를 동시에 고려한 구동력 최소화에 대한 최적화를 수행하였다. 본 연구에서는 조종날개의 공력 및 구조적 특성을 동시에 고려하기 위하여 공력-구조 연계 시뮬레이션을 사용하였으며 공력 및 구조 시뮬레이션에 각각의 전용 소프트웨어를 사용하고자 비정상-약결합 방식 연계기법을 적용하였다. 전역 최적화에는 많은 반복 계산이 필요하므로 빠른 계산을 위하여 수학적 모델링을 이용하였으며 이를 위하여 면 중앙 합성 실험계획법으로 실험점을 선정하였다. 선정된 실험점 및 그에 대한 공력-구조 연계 시뮬레이션 결과를 토대로 2차 다항식 반응면을 생성하였으며 생성된 수학적 모델링을 이용, 유전자 알고리즘 기반 전역최적 설계를 수행하였다. 최적화 목적함수는 마하 0.7 및 마하 2.0 사이의 압력 중심점 이동거리 최소화로 설정하였으며 최적화 결과 압력 중심점 이동거리가 7.5% 감소된 최적형상을 도출하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.660-664
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• 2014

A diesel forklift truck under 3-ton class has disadvantages in the vibration transmission path. Because the weight ratio of body structure to powertrain which is source of excitation force is lower th an a mid-class forklift. In addition, the torsional and bending vibration mode frequencies of body structure are within the engine excitation frequency range, then high idle vibration generated by resonance. In this paper vehicle body structure design and optimization technique considering idle vibration reduction are presented. Design sensitivity analysis is applied to search the sensitive of design parameters in body structure. The design parameters such as thickness and pillar cross section were optimized to increase the torsional and bending vibration mode frequencies.

• 대한기계학회논문집A
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• 제28권10호
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• pp.1558-1565
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• 2004

It is important to determine supporting locations for structural stability when a structure is loaded with non-uniform load or supporting locations as well as the number of the supporting structures are restricted by the problem of space. Moreover, the supporting location optimization of complex structure in real world is frequently faced with discontinuous design space. Therefore, the traditional optimization methods based on derivative are not suitable Whereas, Genetic Algorithm (CA) based on stochastic search technique is a very robust and general method. The KSTAR in-vessel control coil installed in vacuum vessel is loaded with non- uniform electro-magnetic load and supporting locations are restricted by the problem of space. This paper shows the supporting location optimization for structural stability of the in-vessel control coil. Optimization has been performed by means of a developed program. It consists of a Finite Element Analysis interfaced with a Genetic Algorithm. In addition, this paper presents an algorithm to find an optimum solution in discontinuous space using continuous design variables.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1512-1519
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• 2002

Most of mechanical failures are caused by repeated loadings and therefore they are strongly related to fatigue. To avoid the failures caused by fatigue, determination of an optimal shape of a structure is one of the very important factors in the initial design stage. Shape optimization fer two types of specimens, which are very typical ones in opening mode in fracture mechanics, was accomplished by the linear elastic fracture mechanics and the growth-strain method in this study. Also shape optimization for a cantilever beam in mixed mode was carried out by the same techniques. The linear elastic fracture mechanics was used to estimate stress intensity factors and fatigue lives. And the growth-strain method was used to optimize the shape of the initial shape of the specimens. From the results of the shape optimization, it was found that shapes of two types of specimens and a cantilever beam optimized by the growth-strain method prolong their fatigue lives significantly. Therefore, it was verified that the growth-strain method is an appropriate technique for shape optimization of a structure having a crack.

• Steel and Composite Structures
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• 제21권3호
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• pp.501-515
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• 2016

Seismic analysis for steel frame structure with brace configuration using topology optimization based on truss-like material model is studied. The initial design domain for topology optimization is determined according to original steel frame structure and filled with truss-like members. Hence the initial truss-like continuum is established. The densities and orientation of truss-like members at any point are taken as design variables in finite element analysis. The topology optimization problem of least-weight truss-like continuum with stress constraints is solved. The orientations and densities of members in truss-like continuum are optimized and updated by fully-stressed criterion in every iteration. The optimized truss-like continuum is founded after finite element analysis is finished. The optimal bracing system is established based on optimized truss-like continuum without numerical instability. Seismic performance for steel frame structures is derived using dynamic time-history analysis. A numerical example shows the advantage for frame structures with brace configuration using topology optimization in seismic performance.

• 대한토목학회논문집
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• 제5권3호
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• pp.137-144
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• 1985

본 연구에서는 구조물 최적 설계시 필수적인 설계민감도 해석을 의사변분법을 도입하여 유한차원 구조물에 적용함으로써 구조물 최적설계를 기존의 방법보다 훨씬 간편하게 할 수 있음을 보인다. 정하중하에서 제약조건의 주종을 이루고 있는 변위 및 응력의 제약조건에 대하여 설계민감도 해석 및 그 수치해를 구하며 나아가 최적화 알고리리즘을 사용하여 최적설계가 효율적으로 수행됨을 입증한다. 유한차원 구조물인 트러스의 적당한 경계조건, 하중조건 및 제약조건하에서 구조물의 무게를 최소화 시키는 최적설계 문제를 고려한다.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.1022-1035
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• 2016

A double-tube once-through steam generator (DOTSG) consisting of an outer straight tube and an inner helical tube is studied in this work. First, the structure of the DOTSG is optimized by considering two different objective functions. The tube length and the total pressure drop are considered as the first and second objective functions, respectively. Because the DOTSG is divided into the subcooled, boiling, and superheated sections according to the different secondary fluid states, the pitches in the three sections are defined as the optimization variables. A multi-objective optimization model is established and solved by particle swarm optimization. The optimization pitch is small in the subcooled region and superheated region, and large in the boiling region. Considering the availability of the optimum structure at power levels below 100% full power, we propose a new operating scheme that can fix the boundaries between the three heat-transfer sections. The operation scheme is proposed on the basis of data for full power, and the operation parameters are calculated at low power level. The primary inlet and outlet temperatures, as well as flow rate and secondary outlet temperature are changed according to the operation procedure.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.389-395
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• 2016

A Carbon Fiber Composite (CFC) framework was designed for a small lightweight space camera. According to the distribution characteristics of each optical element in the optical system, CFC (M40J) was chosen to accomplish the design of the framework. TC4 embedded parts were used to solve the low accuracy of the CFC framework interface problem. An integrated optimization method and the optimization strategy which combined a genetic global optimization algorithm with a downhill simplex local optimization algorithm were adopted to optimize the structure parameters of the framework. After optimization, the total weight of the CFC framework and the TC4 embedded parts is 15.6 kg, accounting for only 18.4% that of the camera. The first order frequency of the camera reaches 104.8 Hz. Finally, a mechanical environment test was performed, and the result demonstrates that the first order frequency of the camera is 102 Hz, which is consistent with the simulation result. It further verifies the rationality and correctness of the optimization result. The integrated optimization method mentioned in this paper can be applied to the structure design of other space cameras, which can greatly improve the structure design efficiency.